Nondispersive two-electron wave packets in the collinear driven helium atom

Nondispersive two-electron wave packets are found in the Floquet spectrum o f the driven, one-dimensional helium atom. In classical phase space, they a re anchored to the principal nonlinear resonance between the collinear froz en planet orbit and the driving field linearly polarized along the orbit. T hese novel, highly correlated eigenstates of the driven three-body Coulomb problem, exhibit lifetimes of the order of 10(3)...10(7) periods of the dri ving field, with strong fluctuations reminiscent of chaos-assisted tunnelin g.